Press brake



May 19, 1942. Hf F. MacMlLLlN raT/u PRESS BRAKE 5 Sheets-Sheet 1 Filed July 23, 1940 'HET-l hun.,

WEA/rais 'i How/mur fum/aw Paz/L c; mrow I y 4 A t n l ATTORNEYS May 19, 1942- H. F. Macwnl.| n-xA Erm. 2,283,447

PREss BRAKE I Filed July 23, 1940 l s sheets-sheet 2 PAUL C. P06061( irkgnf/m May 19, 1942.

EEE

FORCE /N TO/YS H. F. MacMlLLlN ETAL 2,283,447

PRESS BRAKE Filed July 23, 1940 s sheets-sneek s f 0F PLATE/V ATTORNEYS atenie'd @y gg, 42 Y Howard F. MacMillin and Paul C. Fok, omit .i fl' to me 5 i Development corporation, me., Wil, nel..

a corporation of 1r.. Application July 23, 194e,

-This invention relates to presses and in particular to presses having a long and narrow platen.

It ls an object of the invention to provide a hydraulic press having a long and narrow platen in which any substantial tilting movement of the platen is automatically prevented.

It is a further object of the invention to provide a hydraulic press with a relatively long and narrow platen in which hydraulic means are provided for synchronizing the movement of the ends of the platen. a

A still4 further object of theinvention consists in the provision of a hydraulic press in which a single ram is connected with the central portion of a relatively long and narrow platen, While hydraulic balancing means are connected with the platen ends for preventing any substantial movement of the platen in the direction of the longitudinal axis thereof.

Still anotherobject of the invention consists in the provision of a hydraulic press in which a long and wide platen is reciprocable by a ram ,arrangedl centrally thereof, while the platen ends have associated therewith hydraulicmeans for preventing any substantial tilting movement in the longitudinal direction of the platen and transverse thereto.

A still further object of the invention consists in the provision of'a hydraulic press in which a long and wide platen is reciprocable by a ram having connected therewith, at each corner thereof, hydraulic balancing means for preventing tilting movement of the platen in any direction irrespective of the location of the load relative to the ram,

These and other objects and advantages of the invention will appear more clearly from the following speclncation in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic illustration of 'a press according to the invention.

Figure 2 illustrates a pressing platen having centrally connected therewith the pressing ram, while being connected at the lower surface thereof with two balancing cylinder-piston-assemblies.

Figure 3 is a view similar to Figure 2, however. with the provision of one balancing cylinder-plston-assembly at each corner of the platen.

Figure 4 is a diagrammatic illustration of the distribution of the forces acting upon the platen.

Figure 5 illustrates, by means of a graph, the variation of the forces acting upon lthe platen in (Cl. Nil-71) .ing means.

General arrangement ton-assemblies which are hydraulically interconnected in such a manner that when one end of the platen tends to run ahead oi the other platen end,y the uid pressure in the cyllnder-piston-assembly adjacent the first mentioned platen end is conveyed to the cylinder-piston-assembly adjacent the other platen end so as to retard the latter, thereby re-establishing uniform movement of the platen ends.

Structural arrangement 1 The press illustrated in Figure 1 comprises a main cylinder I, having reciprocably mounted therein a double-acting pressing piston 2, which is connected by means of the ram 3 andLscrews 4 with the central portion of the pressing platen E. Connected-with the main cylinder I and supported thereby is a fluid reservoir or surge tank iilled with fluid 1. The fluid 1 is held under pressure by means of a compressor a operatively lconnected with a motor 9 by means of a belt III and adapted to supply compressed air through the pipe II into the surge tankl 6. The 'surge tank 6 comprises a main cylinder relief and pump b y-pass valve I2 which is connected by means of a conduit I3 with the upper portion of. the cylinder I, while another conduit I4 leads from said main cylinder relief and pump by-pass valve I2 to a surge valve, generally designated I5,

arranged in the upper portion of the cylinder I and adapted selectively to allow uid to passl from the surge tank 6 through the openings I6 into the upper portion of the cylinder I and vice Versa.

The main cylinder relief and pump by-pass valve I2 and the surge valve i5 do not yform a part of the present invention and merely serve to prell the upper portion of the main cylinder I when the piston 2 moves downwardly by gravity during the ilrst portion of its working stroke and to facilitate initiation of the retraction stroke at the end of the working stroke of piston 2. For a more detailed description lof the surge valve I5 and the main cylinder relief and piece relative to the platen.

pump by-pass valve I2, reference may be had to U. S. Patent No. 2,193,248 to Ernst, issued March 12, 1940, and the Ernst patent application, Serial No. 286,063, filed July 24, 1939.

Connected with the surge tank 6 is, furthermore, a conduit l1 leading to a tonnage control valve I8 which, in its turn, is adapted to effect communication between the conduit I1 and a conduit I9, leading to the upper portion of,` the cylinder I. The tonnage control valve I3 is arranged in an electric circuit which comprises a l solenoid 20 associated with the -servomotor 2| A22 through the conduit 25 into the upper portion of the main cylinder I.

When the solenoid 2|! is de-energized a spring 26, connected to the cylinder l, urges the linkage 25 into the opposite direction, thereby moving the flow control member of the variable delivery pump 22 into full stroke reverse position. In this instance pressure fluid is delivered from the pump 22 through the conduit 2'I into the lower portion of the main cylinder I. f

The tonnage control valve I8 which, as previously mentioned, is arranged in the same circuit as the solenoid 20, is adapted to be actuated by a predetermined pressure acting upon the upper surface of the piston 2 so that, at the attainment of said predetermined pressure, the tonnage control valve I8 breaks the said circuit. The tonnage control valve I3 in itself does not form a partof the present invention and for a more detailed description thereof, reference may be had .to U. S. Patent No. 2,224,957 to Ernst.

Branching off from the conduit 2l is a conduit 28 leading to the uid tank '5 and comprising a check valve 29 arranged in the tank 6. The pur- .pose of the check valve 29, in connection with the conduit 28, consists in supplying additional fluid to the suction side of the pump 22 during the irst portion of the downward movement of the piston 2.

Further communicating with the tank is a conduit 30 which comprises a check valve 3| and leads to the upper portion of a balancing cylinder, generally designated 32. The balancing cylinder 32 comprises a cylinder bore 33 having reciprocably mounted therein a double-acting plston 34.- The double-acting piston 34 carries a piston rod 35 passing with its lower end through the bottom of the cylinder 32, while the upper end of the piston rod 35passes through the top portion of the cylinder 32 and is connected by any convenient means, for instance, screws 36, with one end of the pressing platen 5. The other platen end is similarly connected by means of a screw 31 with the piston rod 38 of a double-acting piston 33 reciprocably mounted in a second balancing cylinder, generally designated 40. The upper portion of the cylinder bore 33, pertaining to the cylinder 32, is connected by means of a conduit 4| with the lower portion of the cylinder bore 42 pertaining to the balancing cylinder 40. In a similar manner the upperportion ofthe cylinder bore 42 pertaining to the balancing cylinder 40 is connected by means of a conduit 43 with the lower portionof the cylinder bore 33 pertaining to the balancing cylinder `32. The upper portion of the cylinder bore 42 is, furthermore, connected by means of a conduit 44, comprising a check valve 45, with the iiuid tank 6. The arrangement of the conduits 30 and 44, in connection with the check valves 3| and 45, has the purpose of. maintaining the balancing cylinders 32 and 40 filled with fluid. It is, of course, understood that the necessary provisionsare made to prevent leakage from the cylinders 32, 40, ailing the piston rods 35 and 38 toward the outs e.

While, according to the embodiment of Figures 1 and 2, only two balancing cylinders are provided adjacent each end. it is often advantageous, particularly when long and wide pressing platens are employed, to provide one balancing cylinder at each corner of the platen. Such an arrangement is illustrated in Figure 3 from which it will be noted that only the diametrcally arranged cylinders are connected with each other. In other words, the cylinder 4B at the,rear lefthand corner ofthe platen 61 is connected by conduits 48 and 49 with the front right-hand cylinder 50. The arrangement of the conduits 48 and 49, with respect to the pistons in the cylinders 46 and 50, fully corresponds to the arrangement of theconduits 4I and 43, with respect to the pistons 34 and 39 of the cylinders 32 and 40. Similarly,

the left-hand front cylinder 5I is connected by Operation Assuming that all parts of the press occupy the position illustratedin Figure `1 which corresponds to the position at the end of the retraction stroke of pistion 2, and that it is now desired to start a working cycle, the operator starts the motor 9 for driving the compressor 8 in any convenient manner, which supplies compressed air to the tank 3, thereby putting the fluid in the tank 6 under pressure. As a result thereof, pressure uid will pass through the conduits 30 and dit into the upper portion of the cylinders 32 and l0 respectively in case the upper portion of said cylinders should not be sufficiently filled with fluid. Similarly, the pump 22 is started. Thereupon the Clut Comprising the solenoid 20 and tonnage control valve I8 is closed with the result that the armaturel 23, pertaining to the solenoid 20, is actuated so as to `shift the flow control member of the variable delivery pump 22 into full stroke forward position. piston 2 is now-moving downwardly by gravity,

' iiuid is passed by the pump 22 throughthe conduit 25 into the upper portion of the cylinder I where, it is supplemented by fluid from the tank 6 which passes through the openings I6 of the surgevalve I5. As soon as the platen 5 engages the work piece, pressure builds up in the upperl While the' maten end adjacent the ynnder it win tend to advance more rapidly than the platen end adjacent the cylinder 32. 'Ihis is, however, prevented cylinder dll` can advance only when uid below the piston 39 is adapted to escape into the upper portion of the cylinder bore 33 above the piston 3l pertaining to the balancing cylinder 32. In other words, if the piston 86 is stopped for a fraction of a second due to the resistance exerted by the work piece, the'pressure built up in the cylinder bore 42 below the piston 39, due to the advancing tendency of the piston-39, is conveyed to and held in the upper portion of the cylinder bore 33, thereby braking or retarding the movement of the piston 39 and establishing synchronous movement of the platen ends. As soon as the piston 2 has reached the end of its working stroke, the pressure acting upon the piston 2 has increased to such an extent that it opens the tonnage control valve I3, thereby breaking thevcircuit comprising the solenoid and establishing communication between the conduits l2 and l1. The breaking of the said circuit results in a deenergization of the solenoid 20 so that the spring 26, acting upon the linkage 2t, shifts the ow control memberof the variable delivery pump 22 to full stroke retraction position. Consequently, the conduit 21 is now connected with the pressure side of the pump '22, whereas the conduit 25 is now connected with the suction side of the pump 22. The main cylinder relief and pump by-pass valve I2 now comes into action and relieves, in cooperation with the surge valve I5, the pressure in the upper portion of the cylinder l. Pressure fluid delivered by the pump 22 by the fact thatl the platen end adjacent the i through the conduit 21 acts upon the retraction e side of the piston 2, thereby liftingthe latter together with the platen 5. Upward movement of the platen 5 causes upward movement of the pistons 34 and 39 so that fluid expelled by the piston 34 will flow through the conduit dl and ll the space below thepiston 39 during the advancement of the latter, whilethe iluid expelled by the piston 39 through the conduit t3 will fill the space below the piston 36 during the upward movement of the latter. no fluid lexpelled by the pistons 3e and 39 during the upward movement thereof can escape through the conduits and M respectively into the tank 6, since this escape is closed ofi by the then closed d check valves 3l and d5. Inasmuch as no material pressure acts upon the platen 5 during its upward movement, no tilting movement of the platen 5 will occur.

As soon as the pressure acting upon the piston 2 during its downward stroke has been released, the contacts of the tonnage control valve IB will again close, while the circuit comprising the tonnage control valve and the solenoid 20 remains open. When the piston 2 has reached the end of its retraction stroke, the flow control member of the variable delivery pump 22 is: actuated by any convenient means so as to move either to neutral position, in which case the press would come to a standstill, or, if full automatic operation is desired, thevflow control member of the variable delivery pump 22 will be shifted to full stroke forward position so as to start a new cycle.

As will be seen from the foregoing description, the operation of the press and of the balancing cylinders in particular, will be the same whether the platen is associated with two balancing cyl- It will be noted that inders 32, do, or with four balancing cylinders t6, 50, 5i and 5d. '.l'he only ,difference would be that the arrangement illustrated in Figure 2 would take care of a tilting movement along the longitudinal axis of the platen only, whereas the arrangement of Figure 3 would take'care of a tilting movement of the platen @l in whatever direction it may occur. As previously stated, in the last mentioned arrangement, always two balancing cylinders work together, namely, those diametrically arranged with respect to each other, while no hydraulic communication exists between those cylinders which are not diametrically arranged relative to each other.

To more clearly illustrate the forces exerted upon the platen by the balancing cylinders on one hand and the ram 3 on the other hand, reference may be had to Figures 4 and 5 of the drawings. In these gures F is the force exerted by the ram 3 upon the platen 5, while f1, f2, are the forces exerted by the balancing pistons 3d and 39 respectively. Since the balancing cylihdersv 32 and are of the same construction and diameter and are interconnected by the conduits d3 and 4I, f1 will equal f2. Suppo'sing that F. is tons and that the work piece W is placed six feet from the axis of the left-hand balancing cylinder and fourteen feet from the axis of the right-hand balancing cylinder, while the disltance of the a-xis of the work piece W and the Using the same forces as illustrated in Figure 4, but shifting the work piece W so that its distance from the axis of the left-hand' balancing cylinder is eight feet and from the axis of the right-hand balancing cylinder is twelve feet,

while the distance between the axis of the work piece W and the axis of the ram 3 isv two feet,

the acting forces can be expressed by the following equation:

f1 r 8+f2 12=F 2 Marking the values of f1 and f2 of the above two equations in the graph of Figure 5, it will be seen that all values of f1 and similarly of f2, lie on two straightlines intersecting each other in the center of the platen. In other words,` the balancing forces increase in accordance with the increasing distance between the axis of the ram 3 and the axis of the work piece W. The force F remains the Vsame irrespective of the location of the work piece.

Although the invention has been illustrated in connection with a press in which the balancing cylinders are located below the pressing platen, it will be obvious that the balancing cylinders may also be arranged above the pressing platen without lailecting the scope of the invention.

It will be understood that we desire to comprehend within our invention such modifications as come within the scope of the claims and the invention.

Having thus fully described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a hydraulic press, a pressing platen,hy

draulic motor meansy operatively connected. with the center portion of said platenl for reciprocating the latter, a iiuid source adapted to supply pressure iluid to said motor means for actuating the same, a plurality of hydraulically operable cylinder-piston-assemblies for preventing tilting movement of said-platen, each of said balancing cylinder-piston-assemblies having a double acting piston with equal piston areas and being associated with one corner of said platen, and conduit means interconnecting opposed piston areas equal piston areas and being adapted to be operated hydraulically, conduit means adapted to effect communication between said tank and each cylinder of said balancing cylinder-pistonassemblies, fluid pressure means for exerting a predetermined minimum pressure on the iuid in said cylinders, said minimum pressure being independent of the pressure created by said pumping means, and further conduit means interconnecting opposite sides of separate balancing pistons for securing synchronous movement of the ends of said platen.

3. In a hydraulic press, a pressing platen, hydraulic motor means associated centrally of said platen and operatively connected therewith for reciprocating the platen, pumping means for supplying pressure iiuid to said hydraulic motor means for actuating the same, a plurality or balancing cylinders associated with said platen and having reciprocably mounted therein a double acting balancing piston with equal opposed'piston areas, additional fluid pressure creating means independent of said pumping means .i'or maintaining a predetermined minimum pressure in said balancing cylinders, means adapted to eifect communication between said additional iluid pressure creating means and said balancing cylinder means in a direction 'from said additional iluid pressure creating means to said bal.

ancing cylinders, but not vice versa, and means adapted to convey fluid pressure created on one side oi' one balancing piston to the opposite side oi' another balancing piston for preventing tilting movement ofv said platen.

4. In a. hydraulic press, a pressing platen, hydraulic motor means arrangedv centrally of said platen and adapted to reciprocate the same, -ilrst fluid pressure creating means for supplying pressure iiuid to said hydraulic motor means, hydraulically operable balancing cylinder-pistonassemblies mounted on the opposite sides of said platen adjacent the ends thereof, iluid storage` means, second iluid pressure creating means independent of said first fluid pressure creating means for causing said fluid storage means to supply pressure iluid to and for maintaining said balancing cylinder-piston-assemblies filled with iluid, each o`f said balancing cylinder-piston-assemblies comprising a single cylinder with a double-acting piston of equal opposed piston areas,

and means hydraulically interconnecting opposite sides of separate balancing pistons for prelventing tilting movement of said platen.

HOWARD F. MACMILLIN. PAUL C. POCOCK. 

